Discardable rotating band



March 11, 1969 W. F. KAUFMANN, JR

DISCARDABLE ROTATING BAND Filed Jan. 24, 1968 8M4 d. I

A2 TORNEYS Ficc 1 Claim ABSTRACT F THE DISCLOSURE A gas operated discardable rotating band assembly for projectiles is provided with a chamber for the storage of projectile propulsion gases which separate the assembly from the projectile upon emergence of the projectile from a gun barrel.

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

The weapon art is replete with projectile spin imparting devices which are designed to separate from the projectile while in flight. These devices, commonly known as sabots, generally employ centrifugal forces acting on radially weakened sections to achieve separation. The disadvantages of these devices lie in the complexity of their structure and the high manufacturing costs concomitant therewith.

It is, therefore, an object of this invention to provide a simple and inexpensive discardable rotating band assembly which facilitates projectile manufacture.

Further objects, features, and advantages may be seen by a perusal of the accompanying specification taken in conjunction with the following drawing which is a sectional view along a projectile longitudinal axis showing a typical projectile embodying principles of the invention.

A projectile body 10, shown positioned in a gun barrel A, has a tapered forward nose portion 11 and a tapered rearward portion 13. Forward portion 11 is drilled and tapped at 12 to receive a conventional arming or fuzing device, not shown.

Projectile body portion 13 is rearwardly tapered aft of its maximum diameter 17A to form a frustrum which has a minor surface 17 located transversely to projectile longitudinal axis A-A. Along the intersection of tapered surface 13 and minor surface area 17, a typical radius 21 is formed. Radius 21 reduces stress concentrations in the projectile rearward portion as well as enhances the flight characteristics of the projectile.

A cylindrically shaped rotating band casing 14, preferably made from steel, is internally tapered to mate with projectile tapered surface 13. This internal taper permits casing 14 to be forced or pressed onto projectile rearward portion 13 to facilitate projectile manufacture. Casing 14 has grooves 15 in its outer peripheral surface which grooves receive rotating band 16. Rotating band 16 is preferably made from a soft metal such as brass or copper, however other conventional band materials may be used where warranted by particular design considerations.

A chamber 19 is formed between projectile minor surface 17 and a centrally offset inner surface portion 18 of the transverse casing wall 22. As a skilled artisan would readily perceive, casing wall 22 must be of sufficient strength to withstand combustion pressures with particular design parameters depending upon various factors including combustion pressures, projectile accelerations and the like. Chamber 19 communicates with the projectile exterior through port or vent 20 which is located in casing wall 22 coaxial with projectile axis A-A.

Port 20 has a diameter large enough to permit propulsion gases to be bled into chamber 19 and to achieve equilibrium with propulsion gases acting on casing outer surface 23 prior to emergence of the projectile from the gun barrel. Its diameter must also be small enough to retain the gas pressure in chamber 19 until that pressure separates the casing from the projectile. To achieve these results port diameters should not exceed of the maximum diameter of the projectile nor should they be less than /34 of the projectile maximum diameter.

In operation, projectile 10 and an appropriate pro-pellent charge are placed in a suitable gun and the propellant is detonated. Gases formed by the detonated propellant exert a pressure on hand casing surface 23 to urge the projectile outwardly of the gun barrel. A portion of these gases is bled into chamber 19 through port 20 substantially simultaneously upon detonation, and the pressure of the propulsion gas Within chamber 19 rapidly reaches equilibrium with the gas pressure acting on casing surface 23. The gas within chamber 19 remains under this pressure equilibrium until the projectile leaves the barrel at which time the pressure acting on surface 23 is reduced to atmospheric while the pressure in chamber 19 is substantially unchanged. This pressure differential exerts a force between casing surface 18 and projectile surface 17 which overcomes the frictional forces of the press fit to urge casing 14 rearwardly apart from the projectile. The assembly, thus separated from the projectile, falls to earth.

I claim:

1. In a gun barrel containing a projectile, said barrel having a substantially uniform cylindrical internal surface, said projectile having a tapered forward nose portion and an inwardly and rearwardly tapered rearward portion terminating in a closed rearward end, the combination with said projectile of a discardable rotating band assembly comprising a rigid cylindrically shaped casing of steel construction slidably mounted within said barrel internal surface and having an open forward end and a portion adjacent said open end in frictional engagement with said projectile rearward tapered portion, said casing defining a gas storage chamber located intermediate said casing closed rearward end and said projectile closed rearward end, said casing closed rearward end having a vent for communicating said chamber with the projectile exterior.

At least one rotating band secured to said casing outer peripheral surface for operatively engaging said gun barrel,

pyrotechnic means for producing a gas to propel said projectile through said gun barrel, said gas being bled into said chamber through said vent while said projectile is within said barrel, said gas within said chamber maintaining sufficient pressure to overcome said frictional engagement and detach said casing from said projectile upon emergence of said projectile from said gun barrel.

References Cited UNITED STATES PATENTS SAMUEL W. ENGLE, Primary Examiner.

US. Cl. X.R. 10 293 

